Possible excitonic phase of (Pr1-yRy)1-xCaxCoO3 (R = Lanthanides and Y)

Moyoshi, Taketo; Kamazawa, Kazuya; Matsuda, Masaaki; Sato, Masatoshi

doi:10.1016/j.physb.2017.11.055

Title: Possible excitonic phase of (Pr_1-yR_y)_1-xCa_xCoO₃ (R = Lanthanides and Y)

Abstract

(Pr_1-yR_y)_1-xCa_xCoO₃ (R = Y and/or Lanthanide elements) exhibits a “hidden order transition” in the (x, y) region near (0.5, 0.0) at temperature T_s, where none of magnetic ordering and change of the space group have been found, even though significant anomalies in various physical quantities exist. When the (x, y) is outside of the above region, the transition can essentially be understood by the spin-state-crossover of isolated Co atoms. To study whether excitonic condensation (EC) recently proposed is relevant to the “hidden order transition”, we measured magnetic excitation spectra χ” (Q, ω) by means of inelastic neutron scattering on a single crystal of (Pr_0.8Y_0.2)_0.7Ca_0.3CoO₃, and obtained following results: While the spectra from the Co 3d electrons observed at 200 K (>above T_s) have characteristics of ordinary strongly correlated electron systems, the χ” (Q, ω) - ω curve at 4 K (<T_s) has a feature reminiscent, at first sight, of a weak pseudogap-like structure. This result can be explained by the realization of the EC phase or “EIQ” phase or at least by the picture that the system is in the boundary region between the low-spin and EQI"phases. Finally, this result strongly suggests that there exists the EIQ phase in themore »« less

Authors:

Moyoshi, Taketo ^[1]; Kamazawa, Kazuya ^[1];

^[2]; Sato, Masatoshi ^[3]

Comprehensive Research Organization  for Science and Society (CROSS), Ibaraki (Japan)
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Nagoya Univ., Nagoya (Japan)

Publication Date:: Thu Nov 23 00:00:00 EST 2017

Research Org.:: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:: 1489095

Grant/Contract Number:: AC05-00OR22725

Resource Type:: Accepted Manuscript

Journal Name:: Physica. B, Condensed Matter

Additional Journal Information:: Journal Volume: 551; Journal Issue: C; Journal ID: ISSN 0921-4526

Publisher:: Elsevier

Country of Publication:: United States

Language:: English

Subject:: 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Excitonic condensation; Perovskite cobalt oxides; Hidden order; Magnetic excitation spectra; Neutron scattering

Citation Formats


                    Moyoshi, Taketo, Kamazawa, Kazuya, Matsuda, Masaaki, and Sato, Masatoshi. Possible excitonic phase of (Pr1-yRy)1-xCaxCoO3 (R = Lanthanides and Y).  United States: N. p., 2017. 
Web.  doi:10.1016/j.physb.2017.11.055.

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                    Moyoshi, Taketo, Kamazawa, Kazuya, Matsuda, Masaaki, & Sato, Masatoshi. Possible excitonic phase of (Pr1-yRy)1-xCaxCoO3 (R = Lanthanides and Y).  United States.  https://doi.org/10.1016/j.physb.2017.11.055

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                    Moyoshi, Taketo, Kamazawa, Kazuya, Matsuda, Masaaki, and Sato, Masatoshi. Thu .  
"Possible excitonic phase of (Pr1-yRy)1-xCaxCoO3 (R = Lanthanides and Y)".  United States.  https://doi.org/10.1016/j.physb.2017.11.055.  https://www.osti.gov/servlets/purl/1489095.

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@article{osti_1489095,

  title        = {Possible excitonic phase of (Pr1-yRy)1-xCaxCoO3 (R = Lanthanides and Y)},

  author       = {Moyoshi, Taketo and Kamazawa, Kazuya and Matsuda, Masaaki and Sato, Masatoshi},

  abstractNote = {(Pr1-yRy)1-xCaxCoO3 (R = Y and/or Lanthanide elements) exhibits a “hidden order transition” in the (x, y) region near (0.5, 0.0) at temperature Ts, where none of magnetic ordering and change of the space group have been found, even though significant anomalies in various physical quantities exist. When the (x, y) is outside of the above region, the transition can essentially be understood by the spin-state-crossover of isolated Co atoms. To study whether excitonic condensation (EC) recently proposed is relevant to the “hidden order transition”, we measured magnetic excitation spectra χ” (Q, ω) by means of inelastic neutron scattering on a single crystal of (Pr0.8Y0.2)0.7Ca0.3CoO3, and obtained following results: While the spectra from the Co 3d electrons observed at 200 K (>above Ts) have characteristics of ordinary strongly correlated electron systems, the χ” (Q, ω) - ω curve at 4 K (<Ts) has a feature reminiscent, at first sight, of a weak pseudogap-like structure. This result can be explained by the realization of the EC phase or “EIQ” phase or at least by the picture that the system is in the boundary region between the low-spin and EQI"phases. Finally, this result strongly suggests that there exists the EIQ phase in the present sample or at least in (Pr1–yRy)1–xCaxCoO3 with (x, y) near (0.5, 0.0).},

  doi          = {10.1016/j.physb.2017.11.055},

  journal      = {Physica. B, Condensed Matter},

  number       = C,

  volume       = 551,

  place        = {United States},

  year         = {Thu Nov 23 00:00:00 EST 2017},

  month        = {Thu Nov 23 00:00:00 EST 2017}

}

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https://doi.org/10.1016/j.physb.2017.11.055

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Fig. 2: Examples of the data analysis. At 200 K, the Lorentzian spectral shape ħΓ_Qω/[ħ²ω ²+Γ_Q2] (thick dashed line) is fitted to the observed data (open squares). At 4 K, the sum of the spectra from Co electrons with the shape ħΓ_Qω/[ħ²(ω - ω_Q)² + Γ_Q²] (thick solid line) andmore »

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Title: Possible excitonic phase of (Pr1-yRy)1-xCaxCoO3 (R = Lanthanides and Y)

Abstract

Citation Formats

Figures / Tables:

Title: Possible excitonic phase of (Pr_1-yR_y)_1-xCa_xCoO₃ (R = Lanthanides and Y)